The invention relates to organic inhibitor treating solutions and a method for using such solutions to reduce corrosion from the harsh fluid environments encountered in the oil field. More particularly, the invention concerns treating solutions containing an ethoxylated, propoxylated dialkylphenol amine, which are effective in reducing sweet and sour corrosion.
Corrosion that occurs in an oil field environment is extremely complex and tends to attack all manner of metal equipment above and below ground. The principle corrosive agents found in the well fluids include hydrogen sulfide, carbon dioxide, oxygen, organic acids and solubilized salts. These agents may be present individually or in combination with each other. Valves, fittings, tubing, pumps, precipitators, pipelines, sucker rods, and other producing equipment are particularly susceptible. Deposits of rust, scale, corrosion byproducts, paraffin and other substances create ideal environments for concentration cells. Carbon dioxide and hydrogen sulfide induced pitting is encouraged by such deposits. Acidic condensate that collects on metal tubing will also cause pitting. Extreme temperatures and pressures in downhole environments further accelerate corrosion.
Very often as oil fields mature and enhanced recovery methods such as water flooding and miscible flooding are instituted, the concentrations of hydrogen sulfide and carbon dioxide in the well fluids increases dramatically. This increase in concentration and the resultant increase in sweet corrosion or sour corrosion may make older oil fields economically unattractive due to excessive corrosion costs.
Various surfactants have been employed for many years to inhibit corrosion or to improve the performance of certain organic corrosion inhibitor systems. Surfactants are generally added to inhibitor systems to perform the different functions of (1) solubilizing the corrosion inhibitor or other active ingredients, (2) clean the surface of the metal to be protected or treated, and (3) improving the penetration of the active ingredients into the microscopic pores of the metal.
Ethoxylated alcohols and ethoxylated amines of various structures are common surfactants employed in corrosion inhibition systems. Six examples of such surfactant compounds are provided by U.S. Pat. Nos. 3,038,856; 3,110,683; 3,310,496; 3,623,979; 4,435,361 and 4,420,414. U.S. Pat. No. 3,110,683 discloses a series of alkylated, halogenated, sulfonated, diphenyl oxides and U.S. Pat. No. 3,623,979 discloses a series of imidazolinyl polymeric acid amides. The use of dicyclopentadiene sulfonate salts is disclosed in U.S. Pat. No. 4,435,361. Ethoxylated tertiary amines represented by the formula ##STR2## wherein x is about 9-11 and the sum of (y+z) is 2-50 are described and claimed in U.S. Pat. No. 4,420,414. All four of the above corrosion inhibition patents disclose oil-dispersible inhibiting systems which form a film over the metal parts to be treated. They are not water soluble systems.
A water-dispersible corrosion inhibiting system disclosed in U.S. Pat. No. 4,636,256 contains ethoxylated propoxylated alkylphenol amines of the formula ##STR3## wherein R is an alkyl chain with 5 to 12 carbon atoms, x is 3 to 15 and z is 2 to 10.
A copending patent application, Ser. No. 07/137,646, filed Dec. 24, 1987, also discloses the use of a water-dispersible corrosion inhibiting system with alkoxylated alkylphenol amines. It teaches the use of amines with the formula ##STR4## wherein R is a hydrogen atom or an alkyl chain with about 5 to about 12 carbon atoms, R' is an alkyl chain with about 5 to 12 carbon atoms, x is 1 to 20, z is 1 to 20, a is 1 to 20, and b is 1 to 20.